The spatial and temporal expression of specific gene sets is critical for the execution of complex differentiation programs. Improper execution of differentiation programs can lead to developmental defects, embryonic death, or cancer. The long-term goal of this research is to elucidate the molecular mechanisms regulating transient transcription during meiosis in the budding yeast S. cerevisiae. Ume6p represses early meiotic genes (EMG) in mitosis by recruiting the Sin3-Rpd3 histone deacetylase to EMG promoters. EMG gene induction requires the histone acetyltransferase Gcn5p highlighting the importance of protein acetylation in EMG induction. This proposal focuses on the role of Ume6p acetylation in regulating EMG expression. We have discovered that Ume6p destruction is required for EMG induction. Ume6p destruction is restricted to cells entering meiosis suggesting a meiosis-specific pathway that signals Ume6p for degradation. While searching for potential meiosis-specific destruction signals, we found that Ume6p is a substrate for GcnSp. The acetylation of transcription factors has not been demonstrated previously in yeast and has only been described for a few factors in mammalian systems. To understand the role that Ume6p acetylation plays in regulating the EMG expression, the following aims are proposed: Aim1. Determine the acetylation pattern of Ume6p in mitotic and meiotic cells. The first step in elucidating the role of Ume6p acetylation as it relates to EMG repression is to determine which lysines are acetylated in mitotic and meiotic cells. We will characterize the acetylation pattern of Ume6p at EMG promoters in mitotic and meiotic cells using acetylation specific antibodies. Aim2. Characterize the role of GcnSp and RpdSp in Ume6p acetylation and EMG transcription. The requirement of the Ume6p-Sin3p-Rpd3p interaction in mitotic cells, coupled with the requirement of Gcn5p for meiosis, show that acetylation is critical for the regulation of EMG expression. We will identify if the opposing activities of RpdSp and Gcn5p regulate EMG expression by modifying Ume6p. Aim3. Determine how acetylation antagonizes Ume6p-dependent repression. Ume6p acetylation may modulate EMG expression using several functionally redundant mechanisms. We will determine the functional consequences of Ume6p acetylation and relate them to EMG transcription. The long term goal of this research is to determine the molecular mechanisms governing cellular differentiation. Using Ume6p as a model for gene regulation via transcription factor acetylation, we will learn about the processes that govern the proper execution of differentiation programs.